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   难度：Easy
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  <div>
   <h1 class="question_title">
    682. Baseball Game
   </h1>
   <p>
    You're now a baseball game point recorder.
   </p>
   <p>
    Given a list of strings, each string can be one of the 4 following types:
   </p>
   <ol>
    <li>
     <code>
      Integer
     </code>
     (one round's score): Directly represents the number of points you get in this round.
    </li>
    <li>
     <code>
      "+"
     </code>
     (one round's score): Represents that the points you get in this round are the sum of the last two
     <code>
      valid
     </code>
     round's points.
    </li>
    <li>
     <code>
      "D"
     </code>
     (one round's score): Represents that the points you get in this round are the doubled data of the last
     <code>
      valid
     </code>
     round's points.
    </li>
    <li>
     <code>
      "C"
     </code>
     (an operation, which isn't a round's score): Represents the last
     <code>
      valid
     </code>
     round's points you get were invalid and should be removed.
    </li>
   </ol>
   <p>
    Each round's operation is permanent and could have an impact on the round before and the round after.
   </p>
   <p>
    You need to return the sum of the points you could get in all the rounds.
   </p>
   <p>
    <b>
     Example 1:
    </b>
    <br>
   </p>
   <pre>
<b>Input:</b> ["5","2","C","D","+"]
<b>Output:</b> 30
<b>Explanation:</b> 
Round 1: You could get 5 points. The sum is: 5.
Round 2: You could get 2 points. The sum is: 7.
Operation 1: The round 2's data was invalid. The sum is: 5.  
Round 3: You could get 10 points (the round 2's data has been removed). The sum is: 15.
Round 4: You could get 5 + 10 = 15 points. The sum is: 30.
</pre>
   <p>
    <b>
     Example 2:
    </b>
    <br>
   </p>
   <pre>
<b>Input:</b> ["5","-2","4","C","D","9","+","+"]
<b>Output:</b> 27
<b>Explanation:</b> 
Round 1: You could get 5 points. The sum is: 5.
Round 2: You could get -2 points. The sum is: 3.
Round 3: You could get 4 points. The sum is: 7.
Operation 1: The round 3's data is invalid. The sum is: 3.  
Round 4: You could get -4 points (the round 3's data has been removed). The sum is: -1.
Round 5: You could get 9 points. The sum is: 8.
Round 6: You could get -4 + 9 = 5 points. The sum is 13.
Round 7: You could get 9 + 5 = 14 points. The sum is 27.
</pre>
   <p>
    <b>
     Note:
    </b>
    <br>
   </p>
   <li>
    The size of the input list will be between 1 and 1000.
   </li>
   <li>
    Every integer represented in the list will be between -30000 and 30000.
   </li>
  </div>
  <div>
   <h1 class="question_title">
    682. 棒球比赛
   </h1>
   <p>
    你现在是棒球比赛记录员。
    <br>
    给定一个字符串列表，每个字符串可以是以下四种类型之一：
    <br>
    1.
    <code>
     整数
    </code>
    （一轮的得分）：直接表示您在本轮中获得的积分数。
    <br>
    2.
    <code>
     "+"
    </code>
    （一轮的得分）：表示本轮获得的得分是前两轮
    <code>
     有效
    </code>
    &nbsp;回合得分的总和。
    <br>
    3.
    <code>
     "D"
    </code>
    （一轮的得分）：表示本轮获得的得分是前一轮
    <code>
     有效
    </code>
    &nbsp;回合得分的两倍。
    <br>
    4.
    <code>
     "C"
    </code>
    （一个操作，这不是一个回合的分数）：表示您获得的最后一个
    <code>
     有效
    </code>
    &nbsp;回合的分数是无效的，应该被移除。
    <br>
    <br>
    每一轮的操作都是永久性的，可能会对前一轮和后一轮产生影响。
    <br>
    你需要返回你在所有回合中得分的总和。
   </p>
   <p>
    <strong>
     示例 1:
    </strong>
   </p>
   <pre><strong>输入:</strong> ["5","2","C","D","+"]
<strong>输出:</strong> 30
<strong>解释:</strong> 
第1轮：你可以得到5分。总和是：5。
第2轮：你可以得到2分。总和是：7。
操作1：第2轮的数据无效。总和是：5。
第3轮：你可以得到10分（第2轮的数据已被删除）。总数是：15。
第4轮：你可以得到5 + 10 = 15分。总数是：30。
</pre>
   <p>
    <strong>
     示例 2:
    </strong>
   </p>
   <pre><strong>输入:</strong> ["5","-2","4","C","D","9","+","+"]
<strong>输出:</strong> 27
<strong>解释:</strong> 
第1轮：你可以得到5分。总和是：5。
第2轮：你可以得到-2分。总数是：3。
第3轮：你可以得到4分。总和是：7。
操作1：第3轮的数据无效。总数是：3。
第4轮：你可以得到-4分（第三轮的数据已被删除）。总和是：-1。
第5轮：你可以得到9分。总数是：8。
第6轮：你可以得到-4 + 9 = 5分。总数是13。
第7轮：你可以得到9 + 5 = 14分。总数是27。
</pre>
   <p>
    <strong>
     注意：
    </strong>
   </p>
   <ul>
    <li>
     输入列表的大小将介于1和1000之间。
    </li>
    <li>
     列表中的每个整数都将介于-30000和30000之间。
    </li>
   </ul>
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